Low poly/ cartoonish tropical island creation
What i recommend is to use a tool called Bisect.
To do this,  subdivide a cube and apply Subdivision Surface to get a sphere-ish shape. 
Then to reach the Bisect tool, switch to edit mode, press space, search and there you go.
Press F6 and check "Fill". You can basicly slice pieces from your mesh. Then continue bicecting, till you get the shape you want. Scale the object to perfect your work.
I hope this little tip helped you, if you have any other questions or problems, let me know.

Source: https://youtu.be/G2CdYFgrP84